transform_reduce_range.h

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/***************************************************************************
*   Copyright 2012 - 2013 Advanced Micro Devices, Inc.
*
*   Licensed under the Apache License, Version 2.0 (the "License");
*   you may not use this file except in compliance with the License.
*   You may obtain a copy of the License at
*
*       http://www.apache.org/licenses/LICENSE-2.0
*
*   Unless required by applicable law or agreed to in writing, software
*   distributed under the License is distributed on an "AS IS" BASIS,
*   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
*   See the License for the specific language governing permissions and
*   limitations under the License.

***************************************************************************/

#if !defined( BOLT_AMP_TRANSFORM_REDUCE_RANGE_H )
#define BOLT_AMP_TRANSFORM_REDUCE_RANGE_H

#pragma once

#include <bolt/transform_reduce.h>


#ifdef BOLT_POOL_ALLOC
#include <bolt/pool_alloc.h>
// hacky global var, move to bolt.cpp?
bolt::ArrayPool<HessianState> arrayPool;
#endif

namespace bolt {
    namespace amp {

#define VW 1
#define BARRIER(W)  // FIXME - placeholder for future barrier insertions

#define REDUCE_STEP(_IDX, _W) \
    if (_IDX < _W) tiled_data[_IDX] = reduce_op(tiled_data[_IDX], tiled_data[_IDX+_W]); \
    BARRIER(_W)


    //=======================
    // This version takes a start index and extent as the range to iterate.
    // The tranform_op is called with topLeft, bottomRight, and stride for each section that to be processed by
    // the function.  Function must do iteration over the specified range with specified stride, and also reduce results.
    // May avoid copies on some compilers and deliver higher performance than the cleaner transform_reduce function,
    // where transform op only takes a single index point.
    // Useful for indexing over all points in an image or array
    template<typename outputT, int Rank, typename UnaryFunction, typename BinaryFunction>
    outputT transform_reduce_range(concurrency::accelerator_view av,
        concurrency::index<Rank> origin, concurrency::extent<Rank> ext,
        UnaryFunction transform_op,
        outputT init,  BinaryFunction reduce_op)
    {
        using namespace concurrency;

        int wgPerComputeUnit = p_wgPerComputeUnit; // remove me.
        int computeUnits     = p_computeUnits;
        int resultCnt = computeUnits * wgPerComputeUnit;

        // FIXME: implement a more clever algorithm for setting the shape of the calculation.
        int globalH = wgPerComputeUnit * localH;
        int globalW = computeUnits * localW;

        globalH = (ext[0] < globalH) ? ext[0] : globalH; //FIXME, this is not a multiple of localSize.
        globalW = (ext[1] < globalW) ? ext[1] : globalW;


        extent<2> launchExt(globalH, globalW);
#ifdef BOLT_POOL_ALLOC
        bolt::ArrayPool<outputT>::PoolEntry &entry = arrayPool.alloc(av, resultCnt);
        array<outputT,1> &results1 = *(entry._dBuffer);
#else
        array<outputT,1> results1(resultCnt, av);  // Output after reducing through LDS.
#endif
        index<2> bottomRight(origin[0]+ext[0], origin[1]+ext[1]);

        // FIXME - support actual BARRIER operations.
        // FIXME - support checks on local memory usage
        // FIXME - reduce size of work for small problems.
        concurrency::parallel_for_each(av,  launchExt.tile<localH, localW>(), [=,&results1](concurrency::tiled_index<localH, localW> idx) mutable restrict(amp)
        {
            tile_static outputT tiled_data[waveSize];

#if 1
            init = reduce_op(init, transform_op(index<Rank>(origin[0]+idx.global[0], origin[1]+idx.global[1]),  //top/left
                bottomRight,  // bottomRight
                launchExt));  //stride
#endif

#if 0
            for (int y=origin[0]+idx.global[0]; y<origin[0]+ext[0]; y+=launchExt[0]) {
                for (int x=origin[1]+idx.global[1]*VW; x<origin[1]+ext[1]; x+=launchExt[1]*VW) {
                    init = reduce_op(init, transform_op(concurrency::index<Rank>(y,x)));
                };
            };
#endif

            //---
            // Reduce through LDS across wavefront:
            int lx = localW * idx.local[0] + idx.local[1];
            tiled_data[lx] = init;
            BARRIER(waveSize);

            REDUCE_STEP(lx, 32);
            REDUCE_STEP(lx, 16);
            REDUCE_STEP(lx, 8);
            REDUCE_STEP(lx, 4);
            REDUCE_STEP(lx, 2);
            REDUCE_STEP(lx, 1);

            //---
            // Save result of this tile to global mem
            if (lx== 0) {
                results1[idx.tile[0]*computeUnits + idx.tile[1]] = tiled_data[0];
            };

        } );  //end parallel_for_each
        // results1[] now contains intermediate results which need to be combined together.

        //---
        //Copy partial array back to host
        // FIXME - we'd really like to use ZC memory for this final step
        //std::vector<outputT> h_data(resultCnt);
        //h_data = results1;
        concurrency::copy(*entry._dBuffer, *entry._stagingBuffer);



        outputT finalReduction = init;
        for (int i=0; i<results1.extent[0]; i++) {
            finalReduction = reduce_op(finalReduction, (*entry._stagingBuffer)[i]);
        };

#ifdef BOLT_POOL_ALLOC
        arrayPool.free(entry);
#endif

        return finalReduction;

    };

    template<typename outputT, int Rank, typename UnaryFunction, typename BinaryFunction>
    outputT transform_reduce_range(
        concurrency::index<Rank> origin, concurrency::extent<Rank> ext,
        UnaryFunction transform_op,
        outputT init,  BinaryFunction reduce_op)
    {
        return transform_reduce_range(concurrency::accelerator().default_view, origin, ext, transform_op, init, reduce_op);
    };

    }; // end namespace amp

}; // end namespace bolt


#endif